Commercial and industrial storage tanks are widely used for storing a great variety of liquids. Some of these liquids are highly corrosive and/or are flammable. The service life of a storage tank will vary, depending upon the environmental conditions, including the liquid being stored. Eventually, however, the tank will become corroded and develope leaks. This can result in a significant danger to the environment and health of nearby residents. For example, storage tanks are commonly used for storing gasoline at service stations. Gasoline, of course, is highly flammable and is capable of posing a significant health and safety hazard if not properly contained. Federal as well as local regulations govern the structure of such storage tanks.
Heightened public awareness of the danger posed by storage tanks (particularly underground storage tanks) has led to additional governmental regulations. Recent proposed regulations will soon require most storage tanks to have secondary containment means and possibly a fail safe design feature to guard against accidental soil, water, and air contamination. Secondary containment means must be capable of containing leaked liquid from the storage tank. Bladders within rigid storage tanks have been suggested as one effective means of attaining secondary containment capability. U.S. Pat. Nos. 4,524,609 and 4,552,166 disclose the use of bladders. Double walled tanks have been suggested as another alternative. U.S. Pat. No. 4,523,454 contains one disclosure of a jacketed tank.
Certain storage tanks are designed with a manway on their top surfaces. The manway typically is two to three feet in diameter and has a manhead cover bolted to its top. The manway allows access to the tank's interior for a worker to enter and do any necessary inspections and repairs. The manway opening is also sometimes used as an opening through which a fill line and dispensing line can pass. This type of tank has posed a problem for the aforementioned designs utilizing a secondary containment feature. Thus, a bladder within a rigid tank having a manhead must somehow account for the large opening. Special attachment means must be used to allow easy initial installation and continued use without imparing containment features. Additionally, true secondary containment must include secondary containment for the manway as well as the main storage tank.
There has been developed assemblies for use with storage tanks having secondary containment capabilities. The assemblies use manways of existing tanks with a minimum of change. True secondary containment of the total storage tanks including its manway is achieved.